NotePad XMLValidator

I am using NotePad XMLValidator it checks well the sintax but when I launch my XML agains my .XSD. A pop up appears and says Unknown error, I think maybe there is an incompatibility between the plugin version(1.0.0.1) and the note pad version (6.3.3)

Do you know which versions could work well? Do you know any other open source tool which I could use for this?